We propose structural studies on most available filamentous bacterial viruses, on their intracellular precursor complexes between DNA binding proteins and progeny DNAs, and on the genomes of some. All of the viruses have Gram-negative bacteria as hosts, several of which are pathogenic either in plants or animals. All of the viruses have the same basic overall morphology and all contain a single-stranded DNA genome packed in a sheath of thousands of identical subunits. Techniques such as ultracentrifugation, electron microscopy, light scattering, CD and fluorescence spectroscopy, X-ray diffraction, and other techniques will be applied to determine fundamental structure parameters. Studies on interactions, between intact virions between various virion components, and between the DNA binding proteins and nucleic acids are also proposed. The amino acid sequences of the major structural proteins are to be established through DNA sequencing and protein sequencing techniques. Theoretical work will be directed toward unified theories of the structures of these similar, but in detail diverse, nucleoproteins having the same function, and toward understanding of their evolutionary relationships.